Design, fabrication and high velocity oxy-fuel torch tests of a Cf-ZrB2- fiber nozzle to evaluate its potential in rocket motors

The resistance to ablation of a ceramic nozzle made of a 50vol% Carbon fiber-50vol% ZrB2 composite was evaluated in a high velocity oxy-fuel torch (HVOF) in conditions simulating typical exhaust engine flows. The composite was prepared by hot pressing a mixture of ZrB2 powders and C chopped fibers and characterized in terms of microstructural features, strength and toughness. Then, the sintered pellet was machined by electro-discharge machining to obtain a ceramic throat. The throat was assembled to convergent and divergent graphite parts to compose a segmented nozzle and tested in HVOF torch under a heat flux of 2.5MW/m2 and flame temperature of 2730K. Fluid dynamic simulations enabled to rebuild the heat field temperatures of the jet flow and of the solid nozzle. The throat well survived 30s undergoing little oxidation of the frontal zone without dimension or shape variation. No appreciable ablation of the throat was measured. [Display omitted] •A segmented nozzle composed of divergent and convergent graphite parts and of a ceramic throat was designed.•The ceramic throat with composition 50 vol% Carbon fiber - 50 vol% ZrB2 was machined by EDM from a sintered pellet.•The nozzle was tested in a high velocity oxy-fuel torch (HVOF) in conditions simulating typical exhaust engine flows.•No appreciable erosion of the throat was observed after test at 2.5 Mach supersonic flow and 2730 K flame temperature.